Outline

Introduction: Palmer described in 1938 the ACL to consist out of two functional bundles, namely the anteromedial (AM) and the posterolateral (PL) bundle. When the knee is extended, the PL bundle is tight and the AM bundle is moderately lax. Interestingly, only little is known about the anatomy and the radiological description of the PL bundle. However, a detailed anatomical knowledge of the surgeon is necessary to have the optimal outcome after ACL reconstruction. Aim of the current study was to provide more insight into the anatomy of the ACL with regard to its two functional bundles thereby giving guideline for tunnel positioning in anatomical ACL reconstructions.

Methods: In a total of 20 human cadaveric knees (range 45-87 years) AM and PL bundle of the ACL were identified by their tensioning of the fibres throughout passive flexion and extension. The distances of the centre of AM to the Linea intercondylaris and the PL bundle to the articular cartilage were measured. Radiographic analyses were performed using ap, lateral and Rosenberg views of the femur and ap and lateral views of the tibia and the centre of the bundles described by the techniques of Bernard and Hertel and Harner as well as Harner and Staubli and Rauschning at the femur and the tibia, respectively.

Results: The center of the PL bundle was more shallow and inferior when compared to the center of the AM bundle with a distance of 6.5 mm and a mean of 5.8 mm to the shallow and inferior cartilage margin, respectively. On the tibia, the center of the AM bundle is aligned with the anterior horn of the lateral meniscus, while the PL bundle is 11.2 mm posterior to the anterior horn of the lateral meniscus. According to Bernard and Hertel the center of the AM bundle is at 18.5% and 22.3% and the PL bundle at 29.3% and 53.6%. At the tibia, the centre of the AM bundle is at 30% and the PL bundle is located at 44% according to StÃ¤ubli and Rauschning.

Conclusion: From the anatomical view a double bundle reconstruction mimics the normal structure of the ACL more closely than a single tunnel technique. To reproduce the anatomy, it is mandatory to place the tunnels exactly within the femoral origin and tibial insertion of the ACL.